1. Technical Field
This invention relates to a paper feeder, which is provided as a paper feeding mechanism of an image forming apparatus, for example, and sequentially feeds a number of stacked paper sheets from the top using a paper feed roller, and particularly to the paper feeder, which may surely feed paper sheets one by one without skewing, idle feeding and multi-feeding regardless of the kind of a paper sheet.
2. Description of the Related Art
As a paper feeder for supplying a paper sheet to an image forming apparatus or the like, for example, a known paper feeder is configured so that a number of paper sheets are loaded on a table, the upper most paper sheet is brought into contact with a paper feed roller from below, and the paper sheets are sequentially fed out from the top paper sheet first by the drive of the paper feed roller. In this type of paper feeder, as the height of stacked paper sheets is decreased with feeding out of the paper sheets, the table is elevated to keep the contact between the uppermost paper sheet and the paper feed roller. The paper feeders disclosed in the respective patent literatures described in the following show examples of this type of paper feeder.
JP-A No. 2005-314094 discloses a paper feeder, which efficiently blows out the air to a recording paper sheet with pressure loss of the air held down to thereby simply separate the closely contacting recording paper sheets from each other. In this paper feeder, the position in the right-angled direction to the feeding direction of the recording paper sheet P does not overlap a retard roll 72, and a duct 90 is disposed to overlap the retard roll 72 when viewed in the right-angled direction to the feeding direction of the recording paper sheet P. Thus, the air generated by a blower 94 is blown out to the edge part in the feeding direction of the recording paper sheet P, and the recording paper sheets P fed out from a paper feed tray 44 by a nudger roll 68 are separated by the retard roll 72. The retard roll 72 does not constitute an obstacle so that the duct 90 can be shaped to decrease pressure loss. Therefore, the air enough to release the close contact of the recording paper sheets P is blown out from the duct 90 without using a blower 94 and a fan having a large capacity.
JP-A No. H11-349165 discloses a paper feeder, in which an air current is controlled by an air blowing unit according to the kind of a paper sheet to surely feed paper sheets one by one. This paper feeder includes a paper feed tray 10 on which sheets 23 are piled, a paper feeding unit 2 for feeding the sheets 23 piled on the paper feed tray 10, a push-up unit for pushing up the sheets 23 piled on the paper feed tray 10 by the paper feeding unit 2 towards the height at which the sheets are fed out, a blowing port 21 opened to blow an air current to the side of the sheets 23 pushed up by the push-up unit, a blowing unit 20 for blowing a continuous air current from the blowing port 21, and a blowing position setting unit for setting the air blowing position according to the kind of the sheet 23.
Although the paper feeders described in JP-A Nos. 2005-314094 and H11-349165 are common in that paper sheets in a stack are separated from each other by an air blow and fed out, it is impossible to adjust the quantity of supplied air depending on place such as the right and the left of a paper sheet. Therefore, it is impossible to supply the air quantity adjusted at every required position of the paper sheet according to the state of the loaded paper sheets, resulting in the problem that troubles in paper feeding such as skewing, multi-feeding and idle feeding cannot always be addressed.
This invention has been made in the light of the above circumstances to accurately address the problems in paper feeding such as skewing, multi-feeding and idle feeding by adjusting the quantity of air supplied for every place such as the right and the left of a paper sheet to supply the quantity of air suitable for a required position of the paper sheet according to the state of loaded paper sheets.